More about cygnet
Cygnet “a young swan” was spelled during the Middle English period as signet but is based on Latin cygnus “swan,” plus the French suffix -et “little, small” (as in owlet “little owl” and tablet “little table”). This habit of changing the spelling of words to reflect their origins, also called restored spelling, is hardly limited to cygnet; take a gander at arctic, asthma, debt, homily, horizon, receipt, and symptom, which were respectively spelled in Middle or Early Modern English as artik, asma, dette, omelie, orizonte, receite, and sinthoma but changed to reflect their earlier forms in Latin or Ancient Greek. Despite the spelling of cygnet as signet in Middle English, cygnet is not related to the modern English word signet “a small seal, as on a finger ring,” which is a compound of sign and the suffix -et. Cygnet was first recorded in English in the early 15th century.